Drying apparatus



Oct. 25, 1938. J. c. RE I 2,134,141

' DRYING APPARATUS Filed MarCh 5, 1936 3 Sheets-Sheet l FIIS 'L. 37

INVENTOR 1 JAMEZJ' C. 195A Oct 25, "I938. J. c. REA 2,134,147

DRYING APPARATUS Filed March '5, 1936 QSheets-She'et 2 FIE E 4 Z/ O 52 Z7 INVENTOR JAMES c. ,eE

DRYING APPARATUS Filed March 5, 1936 3 Sheets-Sheet 3 III VIII/III, II/1 7 y INVENTOR 55 56 JAMES C. en?

BY 65 65 FIE E @Q 67 5 v Agj filEY.

Patented Oct. 25, 1938' UNITED STATES- 2,134,147 name arransrns James C. Rea, Oakland, Calif., assignor to Dry Fruit Products Company,

'poration of California Oakland, Calif., a cor- Application March 5, 1936, serial No. 67,193

. 3 Claims.

The invention relates to drying apparatus suclr as used for dehydrating various materials and products, the apparatus of the present invention being used more specifically for the substantially complete desiccation of fruit and other food products. 5 g

An object of the invention is to provide a drying apparatus of the character described which may be constructed in relatively large sizes for handling large quantities of material and; a yet provide aheating system which will insure a uniform application of heat to all portions 01' the material regardless of their position or distribution in the apparatus.

Another object of the invention is to-provide adrying apparatus of the character described in which the heating system is adapted for immediate change for applying heat to or absorbing heat from the material being dried and in either con- 20 dition provide for an improved and increased heat transfer between the heating means and the material. I 1

i A further object of the invention is to provide an apparatus of the character described in which 85 the drying chamber thereof will be simply and fully accessible and into and from which the material to be driedmay be rapidly and readily placed and withdrawn.

Still another object of the invention is to provide a drying apparatus of the character above described having an improved sealing and locking means permitting the use of alternate internal pressures of above and below atmosphere while the drying chamber is hermetically sealed from i the atmosphere. I 7. r

A still further object of the invention is to provide a drying apparatus of the character set forthin which the condensation of moisture on the inner walls of the drying chamber is effectively prevented from re-wetting the material being dried. The/invention possesses otherlobjects and fea-i tures of advantage, some of which, with the foreas going, will be set forth in the following description of the preferred form of the invention which is illustrated in the drawings accompanying and forming part of the specification. It is to be understood, however, that variations in the showing made by the said drawings and description may be adopted within the scope of the invention as set forth in the claims.

Referring to said drawings: Figure 1 is a vertical sectional view of a drying apparatus constructed in accordance with the present invention and shown with an intermediate portion of the apparatus removed.

Figure 2 is a transverse plan sectionalfview of the apparatus shown in Figure 1 and is taken substantially on the plane of line 2-2 of Fig- 5 Figures 3 and 4 are fragmentary side elevations of the apparatus. Figure 5 is a transverse plan sectional view of the base of the apparatus taken substantially on 10 th 'plane'ofline 5-5-of Figure 1.

' Figure'fi is a fragmentary sectional view of a portion of the locking mechanism.

Figure 7 is-a fragmentary side elevation of a part of the locking means. I 15 Figure 8 is a fragmentary sectional view of another part of the locking mechanism.

The drying apparatus of the present invention and as illustrated in the accompanying drawings comprises, in brief, base support ii, a heating system l2 mounted thereon, and an exterior casing l3 which surrounds and encloses the heating system and is likewise mounted on a support ll. The heating system i2 serves a. dual purpose of both heating and supporting the articles or material to be dried in the apparatus and consists \of a plurality of heating tubes M, which are wound back and forth over their length in a sinuous fashion and mounted one over the other to provide a vertical tier of horizontal shelves I5. The tubes are supplied with heating fluidjand, to a large extent, physically supported by a-set of four conduits, i6, l1, l8 and I9, which are generally rectangularly positioned and supported on, and vertically extended from base support Ii. Preferably the conduits provide a relatively large fluid passage and the tubes are individually connected to the-conduits in a plurality of parallel circuits to insure a substantially uniform heating of each of the tubes regardless of its relative position vertically in the apparatus. As will be seen from Figure 2, the shelves, in each instance, may be formed of two complete tubesv each comprising approximatelylone half the shelf. Heating. fluid -is fed from inletconduits I 6 and I! through the 4 coils on'one-half of the shelves,.while inlet conduit i1 and discharge conduit l9 similarly serve the conduits forming the other half of the shelves. The upper ends 26 of the conduits are preferably tubes.

capped and to prevent the entrapping of steam or gas or the like, in these closed ends, a pair of bleeder pipes 21 are connectedby means of a pair of cross-pipes 28 and the upper ends of the conduits. 4

The bent or curved ends 3| of the tubes defin ing the opposite side edges of the shelves are preferably supported by means of cross-bars 32 which are welded or otherwise secured to the ends of each shelf, and arein turn, secured to the upright conduits by means of struts 33. Also secured to the outer sides of the bars are a pair of vertical side walls 35 which defines opposite closed sides between each pair of shelves for a purpose to be more fully hereinafter set forth. In this manner a rigid and sturdy construction of the shelves is provided. When the apparatus is used in connection with the drying of food or similar products, the material to be dried is usually placed upon fiat trays 34 or the like, which may be mounted directly on the shelves.

Substantially any form of heating medium may be used with the present apparatus, such as heated gases, steam,,water and the like, depending to a large extent, upon the temperature desired in the drying chamber. In the drying of certain foods and especially where the desiccation is carried to substantially complete dehydration of the food, it is not infrequent that a critical stage in the dehydrated product is reached and a fixing of the product in this stage is desired. In accordance with the present arrangement, this fixing of the product is made possible by an immediate cessation of the heating process and the substitution of a cooling process, or more specifically the substitution of cold or refrigerated water or the like for the heating medium in the This is facilitated by the connection of the lower ends 29 of the conduits by means of a suitable two-way flow valve (not shown) with the sources of heating and cooling mediums, whereby with the mere turning of a valve an immediate change over from a heating to a cooling cycle or vice versa may be effected.

During the operation of the apparatus and especially where the walls of casing l'3 are appreciably cooled by the surrounding atmosphere a relatively large amount of moisture condenses on the inner sides of the casing walls. In order to prevent this condensate from coming in contact with the material being dried, and causing a re-wetting thereof, a hood 36 is mounted over the top of the shelves and supported on upper I ends 26 of the conduits and serves to catch any thereof to provide a most effective withdrawal of any deposited moisture.

In order that the shelves may be readily and fully accessible for placing material within, or withdrawing same from the drying chamber, the casing 13 is adapted for complete withdrawal from the shelves. This is effected in accordance with the. present invention by hoisting the casing vertically from its seated position to the base and for this purpose, a suitable catch 42 is provided 4 on the top 3'! of the casing for engagement with a hook 43 on a hoisting cable 44. A proper guidance of the casing in its raising or lowering movement may be effected by the use of a plurality of spaced handles 46 on the exterior of the side wall 38 of the casing. Also the lowering operation of the casing is facilitated by the use of a pair of V or Y shaped guides 41, positioned at opposite sides of base II, and which receive a pair of depending members 48 on the casing for guiding the latter to the properly seated position on the base. Also provided in a groove 49 surrounding the top of base II is a compressible gasket 5| which is engaged and compresses by an annular ring 52 on the open bottom end of the casing. Thus, when the drying chamber is under a reduced pressure the greater pressure at the outer side of the casing, plus the weight of the casing itself, will serve to tightly press ring 52 against the gasket 5| and hermetically seal the drying chamber from the atmosphere.

In certain processes, however, it is desirable to increase the pressure in the drying chamber and in some instances, to well above atmospheric pressure, and to hold the casing in sealed position against the base under such conditions, a locking mechanism is used. This mechanism consists of a plurality of radially extending levers 58 mounted within the base H and having their outer ends extended through a plurality of circumferentially spaced openings 59 in the vertical side wall 6| of the base and into engagement with a plurality of circumferentially' aligned U shaped brackets 63 secured to the ring 52 at the lower end of the easing. The inner ends of the levers. are pivoted to spaced flanges 56 and 51 on a hub 54 which is slidably and rotatably carried on an axially extending shaft fixed to the center of the bottom wall 4| of the base. The levers may be extended into engagement with the brackets 63 or retracted therefrom by rotation of member 54 and this operation is provided by the use of lever 64 pivoted to the wall 6| of the base and connected at its lower end by meansofa link 65 to the periphery of the disc 56. With the levers extended into engagement with the brackets 63 a desired .pressure may be exerted against the brackets for drawing the ring 52 of the casing against the sealing gasket 5|- by elevating the inner ends'of the levers and causing the latter to fulcrum on the top surfaces 66 of the openings 59. The raising of the hub 54 and the inner ends of the levers is effected by a nut 61 threaded on the lower end of shaft 53 and supporting the hub through the interpositioning of a thrust bearing 68. The nut 61 may be provided with a peripheral gear 69 which is rotated by a chain 13 connected with a drive gear H which is in turn, operated by a hand-wheel 12. As will be clear from Figures 6 and 8, a small amount of play is afiorded the pivotal connections between the inner ends of the levers and the discs to accommodate the fulcruming of these levers in the openings 59 as aforesaid.

Provisions of certain electrical connections within the drying chamber permitting the use of thermostats and other electrical testing apparatus in the chamber may be afforded by the extension of electrical conductors I6 into the chamber by way of a conduit 14 fixed to the base 4| of the chamber. A hermetic sealing extension of these electrical conductors in the chamber is provided by the extension of the conductors between a pair of compressible gaskets Tl clamped between a plate 18 and a flange I9 on the inne end of the conduit.

One of the most important features of the apparatus is the specific arrangement of the coils l4 defining the individual shelves for supporting and heating the material placed .thereon. As

will be understood the heat may be transferred from the coils to the material by conduction, radiation and convection. I have found that by maintaining a substantially uniform temperature across the width of the shelves, a substantially uniform transfer of heat by conduction and radiation may be realized; but the'transfer of heat by convection is in addition dependent upon the air or vapor currents in the chamber. Normally the pans or trays 34 carrying the material to be dehydrated will occupy substantially the full area of the shelves so that on evacuating the chamber and vaporizing of the moisture in the material, the air and vapor will be confined to a lateral or horizontal outward flow between the shelves. This air and vapor, as will be understood, is further heated during its outward flow by both conduction and radiation of heat from the adjacent upper coils. As a result the outer edges of the material are in addition, heated by these gases, moving outwardly from all parts inwardly of such edges while the material at the center portion of the shelves received little or no heat from these currents. Under such condition there is a graduated increase of heat transfer by convection from the center to the outer sides of the material and which if complemented by uniform heat transfers by conduction and radiation will cause a premature drying and burning of the outer edges of the material. In accordance with the present invention, I compensate for the unequal heating by convection by an opposite gradation of the heat transfer by conduction and radiation, making such transfer largest at the center portion of the shelf and decreasing the same towards the outer sides of the shelves. This may be effected by causing a sufficient temperature drop in the heating medium between the center and the outer ends of the coils or by changing the radiating and conductivity characteristics of the coils by changing their size, material or surface. In the present case, however, I prefer to simply graduate the spacing between the adjacent sides of the coils, increasing from the center to the outer ends. As will be understood this change in spacing will not materially affect the conduction and radiationof heat at the sides 3| of the coils especially at the intermediate portions of such sides. Con- 50 sequently I eliminate the convection of heat in the direction of these sides by confining the escape of the air and vapor from these sides by means of the walls 35 hereinbefore referred to.

I claim: 1. A drying apparatus comprising, a casing providing a drying chamber, heating means dewithdrawing air and vapor from between said shelves, said heating means being arranged to provide a smaller transfer of heat to said material by conduction and radiation at the outer sides of said shelves than inwardly of said sides.

2. A drying apparatus comprising, a casing providing a drying chamber, heating tubes extending transversely across said casing to define a tier of vertically spaced horizontal shelves for supporting the material to be dried, means for withdrawing air and vapor from between said shelves, the tubes comprising each of said shelves being spaced a greater distance adjacent the outer sides of said shelf than adjacent the center of said shelf. I

3. A drying apparatus comprising, a base support, heating means forming a vertical tier of shelves for supporting the material to be dried, an open bottom casing adapted to be lowered into enclosing position about said shelves and onto said support, a means for releasably looking said casing on said support comprising, a threaded shaft depending from the center of said support, a disk rotatably carried on said shaft, said support being provided with a plurality of peripherally spaced openings opposite said disk, a plurality of U-shaped brackets depending from said casing at the outer side of and in substantial alignment with said openings, a plurality of levers pivoted to said disk and radially extended therefrom and into said openings, means operable from the exterior of said base for rotating said disk and causing a radial extension and retraction of said levers into and from engagement with said brackets, a nut threaded on said shaft below and supporting said disk, and means operable from the exterior of said base for rotating said nut and causing an elevation of said disk and a fulcruming of said levers in said openings for depressing said brackets and thereby drawing said casing against said support.

- JAMES C. REA. 

